(1) Field of Invention
The present invention relates to an improved grounding ring for use in grounding adapter devices. The improved grounding ring of the present invention has a vastly larger contact area which provides better capacitive coupling.
(2) Statment of Prior Art
Electrical connectors frequently employ spring devices to provide electrical contact between a cable and a surrounding housing. U.K. Patent No. 1,402,861 to Sutcliff illustrates one such electrical connector. The connector includes a sleeve or housing formed of electrically conductive material anchored to a wall of a box structure and a bush member adapted to co-operate with the housing. The bush member has a central aperture through which a cable such as a coaxial cable is passed. A helically wound spring bent to form a ring is positioned within the sleeve to provide electrical contact between the housing and a portion of the cable. To obtain maximum contact between the spring, the cable and the housing, the spring is compressed by the bush member.
Today, virtually all grounding devices relating to wire, cable, or conduit groundings that are used in relation with stuffing tubes, shield grounding adapters, or conduit grounding fittings, use either soldered, compression, or spring type devices to cause internal grounding. U.S. Pat. No. 3,830,957 to Oberdiear illustrates one such grounding device for a shielded electrical cable. The grounding device includes a pair of relatively soft resilient O-rings, each of which is surrounded by a braided metal sheath, disposed between a cable and a housing. The rings are mounted adjacent oppositely facing bevel rings with a straight sided washer disposed between them. A nut threadedly connected to the housing is tightened to diametrically compress and distort the O-rings and sheaths simultaneously. The sheaths are thus distorted into electrical grounding engagement with the shield of the cable, the bevel rings, washer and an inner housing wall. A similar type of device is illustrated in German Offenlegungsschrift 24 05 241 to Siemens AG. One of the deficiencies of these devices is that the O-rings tend to be permanently compressed thus lessening their ability to provide good electrical contact.
In other types of devices, a toroidally shaped grounding ring such an iris ring is used to provide electrical contact between the electrical cable to be grounded and the grounding adapter or stuffing tube. Swedish Patent No. 131,239 to Sjoholm illustrates such a device. The principal deficiency of these types of grounding rings is the relatively small tangential contact areas which can be subjected to corrosion, contamination, and varying electrical performance depending on the pressures applied to the ring.